The center of the optical sight is below or above the center of view, for the position of the character's doll lying on an uneven piece of land. Whenever I line up my actions relative to the center of focus - the “T” of the crosshair applicable to the object / target, the action — to switch to an iron sight or optical sight — focuses the center of the sight well below or above the object / target. This leads to the fact that the target goes beyond the optical review of the sight of the weapon.
Exit from the action "Sight" has the same effect, the focus of view remains above or below the object / target.
https://youtu.be/llDXxAwcKsw
According to the sensations in the game, the aiming process takes place without tactility for the position of the character's doll body - lying on a non-horizontal piece of land. When I want to look through the sight of a weapon, I lose sight of the object / object of observation.
When you see a point in the middle of the screen - this is the focus of eye vision.
When I raise the weapon, the point on the screen is converted to "T" - they synchronize well.
But when I transfer the line of sight through the sight of the weapon, the "T" does not synchronize with the center of the sight of the weapon.
When the character's doll body does not lie horizontally - the head is above or below the legs.
The greater the slope, the greater the divergence of the centers of eye vision and rifle sight.

For the position of the character's doll "raised" or "sitting", this problem is not.